About 150 National Guard troops are involved in crisis response on the Big Island of Hawaii, where the Kīlauea volcano erupted Thursday and sent a cloud of ash and debris rising to 30,000 feet, a Pentagon official said.

The Hawaii National Guard troops are assisting in fire prevention, air quality tests and traffic control, as well as preparing evacuation plans and providing support to local law enforcement, said Dana White, the Pentagon's chief spokesperson.

Defense Secretary Jim Mattis has put Brig. Gen. Kenneth Hara, deputy adjutant of the Hawaii National Guard, in charge of the crisis response at least through June 14, she added.

At a press briefing on the Big Island on Wednesday, Hara said his troops are involved in getting out the message to residents to "be prepared at a moment's notice that they might have to evacuate."

"What's challenging for us is -- what's going to be the population we're going to need to evacuate by air? I think the worst case is about 1,000," he said, but "some may elect to stay there because they are so self-sufficient."

The eruption at 4:14 a.m. local time at the volcano's summit followed a similar but smaller eruption Tuesday.

The latest eruption opened up more than a dozen fissures east of the crater and came after two weeks of volcanic activity and lava flows that have destroyed at least 26 homes and 10 other buildings but caused no deaths thus far.

"The one this morning was definitely the biggest we've seen so far just in terms of energy and how high up into the atmosphere it got," U.S. Geological Survey volcanologist Michelle Coombs said at a morning press conference.